含白云石微粉水泥砂浆的抗硫酸盐侵蚀性能

Sulfate Resistance of Portland Cement Mortars with Dolomite Powders

为评估白云石微粉对水泥抗硫酸盐侵蚀性能的影响,以石灰石微粉为参照,研究了白云石微粉掺量（质量分数）分别为10%、20%、30%时,水泥砂浆在质量浓度为5%硫酸钠溶液中的变形和强度发展规律,并讨论了基于抗蚀系数的含碳酸盐岩微粉水泥抗硫酸盐侵蚀性能评价方法。结果表明：砂浆试体在Na_2SO_4溶液中的变形过程可分为稳定期、缓慢膨胀期和加速膨胀期3个阶段。除掺10%白云石微粉试体外,其余含碳酸盐岩微粉砂浆的膨胀率均大于空白样（PC）。与掺石灰石微粉试体相比,含白云石微粉试体起始膨胀的龄期滞后,同期膨胀小,且两者膨胀差异随龄期延长和掺量增加呈增大趋势。无论在水中还是在Na_2SO_4溶液中,掺碳酸盐岩微粉砂浆抗压和抗折强度发展趋势均与PC类似,但强度均降低,且掺量越大,强度降幅越大。与在水中养护时强度持续缓慢增长不同,掺碳酸盐岩微粉砂浆强度在Na_2SO_4溶液中经历先快速增长至峰值,而后降低的过程。与含石灰石微粉试体相比,含白云石微粉砂浆强度达到峰值的龄期滞后且后期强度高。标准规定的28 d抗蚀系数K_（28）不能确切反映含碳酸盐岩微粉水泥抗硫酸盐侵蚀性能。采用试体起始膨胀或强度达峰值龄期的抗蚀系数可提高判定结果的准确性和可靠性。

To evaluate the effect of dolomite powder on the sulfate resistance of Portland cement, a comparative study was performed on the sulfate resistance of Portland cement mortars containing dolomite powder（limestone powder as a reference）. The expansion and strength change of mortars with various replacements of dolomite powder（i.e., 10%, 20% and 30%, mass fraction） were investigated in 5% sodium sulfate solution. A method based on sulfate-resisting index for evaluating the sulfate resistance of cement with the carbonate mineral powders was proposed as well. Results indicate that the process of mortars expansion can be divided into three stages, i.e., stable period, slow period and accelerate period. The mortars with carbonate mineral powders except for the specimens with 10% dolomite powder give larger expansion than that of PC. Compared to the mortars with limestone powder, dolomite-containing mortars show a delayed start in expansion and develop a lower expansion at the same age. The difference in expansion is more pronounced with prolonging immersed immersion in Na_2SO_4 solution and the increase of the powder dosages. The mortars with carbonate mineral powders in either water or sodium sulfate solution develop a similar trend with PC, but have lower compressive and flexural strengths. The greater replacement of carbonate powders in mortars, the lower values in the strength. The strength of mortars immersed in water increases, but the strength of mortars in sulfate solution firstly increases and then decreases. Compared to the mortars with limestone powder, the mortars with dolomite powder achieve the maximum strength for a longer time and have a greater strength at later period. The sulfate resistant index at 28 d K_（28） specified in the standard can not accurately reflect the sulfate resistance of the cement with carbonate mineral powders. The sulfate resistance index at the age of starting expansion or reducing attaining peak strength could be applied to improve the accuracy and reliability.